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For the first time, a combined genome-wide transcriptome and metabolic analysis was performed with a dairy Lactococcus lactis subsp. lactis biovar diacetylactis strain under dynamic conditions similar to the conditions encountered during the cheese-making process. A culture was grown in skim milk in an anaerobic environment without pH regulation and with a controlled temperature downshift. Fermentation kinetics, as well as central metabolism enzyme activities, were determined throughout the culture. Based on the enzymatic analysis, a type of glycolytic control was postulated, which was shared by most of the enzymes during the growth phase; in particular, the phosphofructokinase and some enzymes of the phosphoglycerate pathway during the postacidification phase were implicated. These conclusions were reinforced by whole-genome transcriptomic data. First, limited enzyme activities relative to the carbon flux were measured for most of the glycolytic enzymes; second, transcripts and enzyme activities exhibited similar changes during the culture; and third, genes involved in alternative metabolic pathways derived from some glycolytic metabolites were induced just upstream of the postulated glycolytic bottlenecks, as a consequence of accumulation of these metabolites. Other transcriptional responses to autoacidification and a decrease in temperature were induced at the end of the growth phase and were partially maintained during the stationary phase. If specific responses to acid and cold stresses were identified, this exhaustive analysis also enabled induction of unexpected pathways to be shown.Lactic acid bacteria (LAB) are gram-positive microorganisms that have a real economic impact due to their use in many different food transformation processes. The bacterium Lactococcus lactis, which is commonly used as a starter bacterium in the manufacture of different dairy products, such as cheese, butter, and buttermilk, is generally considered a model for metabolism regulation, physiology, and genetic studies in LAB. In industrial conditions, as well as in natural ecological niches (plants, animals, and gastrointestinal tracts), different physicochemical stresses (including acid, thermic, oxidative, and osmotic stresses) are encountered, leading to suboptimal growth. Acid stress turns out to be the major stress that L. lactis is confronted with during fermentative processes. L. lactis, which is generally considered a homofermentative bacterium, is able to convert more than 90% of the sugar metabolized into lactic acid, whose accumulation is responsible for the progressive acidification of the medium, which leads to autoinhibition of lactococcal growth. This process, which is generally attributed to bacterial membrane permeability to the nondissociated form of lactic acid, increases when the medium is acidified and results in a decrease in the internal pH (12). This cytoplasmic acidification is known to be responsible for growth inhibition (11, 21) or a loss of cell viability (10,14,26,30) due to limitation of the activity...

Over 359 million tons of plastics were produced worldwide in 2018, with significant growth expected in the near future, resulting in the global challenge of end-of-life management. The recent identification of enzymes that degrade plastics previously considered non-biodegradable opens up opportunities to steer the plastic recycling industry into the realm of biotechnology.Here, we present the sequential conversion of polyethylene terephthalate (PET) into two types of bioplastics: a medium chain-length polyhydroxyalkanoate (PHA) and a novel bio-based poly(amide urethane) (bio-PU). PET films were hydrolyzed by a thermostable polyester hydrolase yielding 100% terephthalate and ethylene glycol. A terephthalate-degradingPseudomonas was evolved to also metabolize ethylene glycol and subsequently produced PHA.The strain was further modified to secrete hydroxyalkanoyloxy-alkanoates (HAAs), which were used as monomers for the chemo-catalytic synthesis of bio-PU. In short, we present a novel value-chain for PET upcycling, adding technological flexibility to the global challenge of endof-life management of plastics.

This study proposes a thorough investigation, especially based on thermodynamics, to predict phase separation in a linear thermoplastic polyurethane, denoted TPU, prepared from fatty acid-based soft segments and MDI (4,4'-methylene bis(phenyl isocyanate))/BDO (1,4-butanediol) hard segments and specially designed for bitumen modification. Hansen' solubility parameters (HSP) of both segments are evaluated to predict their compatibility. The later ones are evaluated either individually from the corresponding segment synthesized separately or from a decomposition of the solubility diagram of the TPUs into two distinct spheres. In a second step, phase separation is experimentally analyzed by combining differential scanning calorimetry, microscopy techniques, and small angle X-ray scattering (SAXS). The microstructure of the TPUs is described considering one soft phase